FRIDAY, Nov. 22, 2013 (HealthDay News) -- Obese or overweight people who lower their blood pressure, cholesterol and blood sugar levels could cut their risk of heart disease and stroke by more than half, a new study indicates.

Researchers analyzed 97 studies that included a total of more than 1.8 million people worldwide. They found that high blood pressure, cholesterol and blood sugar levels explain up to half of overweight and obese people's increased risk of heart disease. And those same factors account for three-quarters of their increased risk of stroke.

High blood pressure posed the greatest threat, accounting for 31 percent of the increased risk of heart disease and 65 percent of the increased risk of stroke, according to the study, published online Nov. 22 in The Lancet.

"Our results show that the harmful effects of overweight and obesity on heart disease and stroke partly occur by increasing blood pressure, serum cholesterol and blood [sugar]," senior study author Goodarz Danaei, an assistant professor of global health at Harvard School of Public Health in Boston, said in a school news release. Therefore, controlling these risk factors -- for example, through better diagnosis and treatment of high blood pressure -- can prevent some of the harmful effects of overweight and obesity, he added.

Obesity has nearly doubled worldwide since 1980. More than 1.4 billion adults aged 20 and older are overweight or obese. Health problems associated with overweight and obesity include heart disease and stroke -- the leading causes of death worldwide -- diabetes, and several types of cancer.

Moreover, about 3.4 million people worldwide die each year because of overweight and obesity, according to the researchers.

Study co-author Majid Ezzati, a professor of global environmental health at Imperial College London, said controlling blood pressure, cholesterol and diabetes will be "an essential but partial and temporary response" to the obesity epidemic.

"As we use these effective tools, we need to find creative approaches that can curb and reverse the global obesity epidemic," Ezzati said in the news release.